Experimental and computational kinetic evaluations of silver(i)-catalyzed oxidation of p-chlorophenol by hexacyanoferrate(iii): exploring the mechanistic pathway

Abstract

The present investigation delves into the redox reaction between p-chlorophenol (p-CP) and hexacyanoferrate(III) [HCF(III)], catalyzed by Ag(I) in an alkaline environment. Findings reveal a first-order dependence on both p-CP and the oxidant, and the reaction rate showcased a first-order reaction towards Ag(I), which was further amplified by the medium as per the equation k_obs = a + b[OH⁻]. Interestingly, the ionic strength remained unchanged throughout the reaction, exerting no discernible effect on the reaction rate. For the evaluation of activation and thermodynamic parameters, Arrhenius and Eyring equations were utilized. Spectral analysis identified the oxidation product of p-CP as hydroquinone. The exploration was further extended to various organic solvents, with their effects scrutinized through Taft's and Swain's multiparametric equations. Notably, the rate constants failed to correlate satisfactorily with Kamlet–Taft's solvatochromic parameters (α, β, π*). Based on the kinetic findings, a plausible reaction mechanism was proposed, which was further supported by the density functional theory (DFT) calculations performed at the b3lyp/6-311*g (d,p) level. The activation energy values obtained from the DFT results were consistent with the reactivity trends observed in the experimental data, thereby validating the proposed mechanism.